Nonflammable molding compositions of styrene polymers

ABSTRACT

IMPROVED NONFLAMMABLE POLYSTYRENE MOLDING COMPOSITIONS CONTAINING 1-20% OF A BROMINATED POLYALKYLBENZENE OF THE FORMULA   (R)M,(R&#39;&#39;)N-BENZENE   WHEREIN R IS BROMOMETHYL OR DIBROMOMETHYL, M IS AN INTEGER FROM 2 TO 4, INCLUSIVE, R&#39;&#39; IS ALKYL OF 1-3 CARBON ATOMS, BROMINE OR CHLORINE, AT LEAST ONE R&#39;&#39; BEING ORTHO TO EACH R, AND N IS AN INTEGER FRP, 1 TO 4, INCLUSIVE.

United States Patent O 3,817,912 NONFLAMMABLE MOLDING COMPOSITIONS OF STYRENE POLYMERS Klaus Diebel and Helmut Birkner, Marl, West Germany, assignors to Chemische Werke Huls Aktiengesellschaft N Drawing. Filed Dec. 29, 1971, Ser. No. 213,738 Claims priority, application Germany, Dec. 31, 1970, P 20 64 677.9 Int. Cl. C09k 3/28 US. Cl. 260-455 R 15 Claims ABSTRACT OF THE DISCLOSURE Improved nonflammable polystyrene molding compositions containing 1-20% of a brominated polyalkylbenzene of the formula wherein R is bromomethyl or dibromomethyl; m is an integer from 2 to 4, inclusive; R is alkyl of 1-3 carbon atoms, bromine or chlorine, at least one R' being ortho to each R; and n is an integer from 1 to 4, inclusive.

BACKGROUND OF THE INVENTION This invention relates to nonflammable thermoplastic polystyrene molding compositions.

Self-extinguishing and/or nonflammable molding compositions are utilized to an increasing extent in many fields of application, predominantly in the construction, electrical and automotive industries. It is known to employ halogen-containing substances as flame retardants for thermoplastic synthetic resins, and that organic bromine compounds are significantly more eflfective than comparable chlorine-containing compounds. See Thater, Brennverhalten von Plastformstoflen (1968); Vogel, Flammfestmachen von Kunststoflen (1966).

German Published Application DAS 1,201,544 describes flameproof molding compositions which have been rendered flameproof by the addition of 25-40% by weight of chlorinated hexamethylbenzenes, based on the polymer composition, in mixture with oxygen compounds or sulfur compounds of an element of Main Group V of the Periodic Table. However, additives of this order of magnitude have a detrimental eflect on the mechanical properties of the basic polymers. In Canadian Pat. 558,230, nonflammable polystyrenes are described wherein 3- by weight of low-substituted bromination products of alkyl benzenes of 8-10 carbon atoms, e.g., 1,2-di(dibromomethy1)benzene is utilized. However, the aforementioned compounds are too unstable chemically and thermally, so that they cannot be used at the usual, high processing temperatures of ZOO-250 C. in injection molding machines or extruders.

Also, for the same reasons, to, w, w, w'-tetrabromoxylene and the analogous compounds bromine-substituted in the methyl group, such as, for example, w,w'-dibr0- moxylene and w,w,w,w,w',w'-hexabromoxylene, which are described in German Published Application DOS 1,468,- 852 as flame-retarding components for expandable types of polystyrene compositions, are unsuitable as flame retardants in the production of molded articles in injection molding machines or extruders at conventional processing temperatures.

In US. 3,635,850 and German Patent Application P 17 94 182.1-43, bromination products of hexamethylbenzene are proposed as flame retardants for styrene polymers,

3,817,912 Patented June 18, 1974 which products can be employed, if desired, together with organic chlorine compounds and antimony trioxide. The bromination of hexamethylbenzene at a higher temperature results, in correspondence with the amount of bromine utilized, in mixtures of substances containing compounds with 1-6 bromomethyl groups in the molecule. However, these bromination mixtures also contain, in. addition to effective compounds, substances of little or no eflectiveness, so that they must be employed in relatively large amounts to ensure eflicient flameproofness, thereby unfavorably altering the good mechanical properties of the basic polymers. The removal of the compounds of low elfectiveness from the bromination mixture cannot be accomplished technically or only at considerable expense. Nevertheless, it is desirable to employ flame retardants in quantities as low as possible.

It has now been found that nonflammable molding compositions from styrene polymers, which do not exhibit these disadvantages, can be obtained by providing that the styrene polymers contain brominated polyalkylbenzenes as defined hereinafter.

SUMMARY OF THE INVENTION The novel nonfiammable polystyrene molding compositions of this invention contain 1-20%, based on the styrene polymer, of a brominated polyalkylbenzene of the general Formula I wherein R is bromomethyl or dibromomethyl; m is an integer from 2 to 4, inclusive; R is alkyl of 1-3 carbon atoms, bromine or chlorine, at least one R being ortho to each R; and n is an integer from 1 to 4, inclusive.

DETAILED DISCUSSION 1,2-diR-3,6-diR'-benzene, 1,2-diR-3,4,6-triR-benzene, and 1,2-diR-3,4,5,6-tetraR'-benzene;

1,3-diR-2 R'-benzene, 1,3-diR-4,'6-diR'-benzene, l,3-diR-2,'6-diR-benzene, 1,3-diR-2,4,'6-triR'-benzene, and 1 3-diR-2,4,5,6-tetraR'-benzene;

1,4-diR-3,6-diR'-benzene, 1,4-diR-2,3-diR'-benzene, 1,4-diR-2,3,5-triR-benzene, and 1,4-diR-2,3,5,6-tetra-R'-benzene;

1,2,4-triR-3,6-diR'-benzene, and 1,2,4-triR-3,5,6-triR'-benzene;

1,3,5-triR-2,4-diR-benzene, 1,3,5-triR2,6-diR'-benzene, and 1, 3,5 -triR-2,4,6-tri'R-benzene;

1,2,4,5-tetraR-3,6-diR-benzene.

As seen from these classes of polyalkylbrominated benzenes, each R group (BrCH or Br CH) has at least one R group (alkyl of -1-3 C, Br or Cl) ortho thereto.

Specific examples of such brominated polyalkylbenzenes are 1,2,4,5'-tetrakis ('bromomethyl -3 ,6-dibromobenzene; 1,2,4,5-tetrakis (bromomethyl -3 ,6-dichlorobenzene; 1,3,5-tris (bromomethyl) -2,4,6-tribromobenzene;

1,3 ,5 -tris (bromomethyl) -2,4,6-trichlorobenzene;

1,3,5 -tris( bromomethyl) -2,4,6-trimethylbenzene; 1,4-bis (bromomethyl -2,3,5,6-tetramethylbenzene; 1,4-bis(dibromomethyl -2,5-dibromobenzene; 1,4-bis(bromomethyl) -2,5-di'bromobenzene;

1,4-bis( bromomethyl 2,5 -dimethyl-3,6-dibromobenzene; 1,4-bis(bromomethyl -2,5-dimethylbenzene;

1,4-bis (bromomethyl -2,5-diethylbenzene;

1,3-bis (bromomethyl -4,'6-dimethylbenzene; 1,3-bis(bromomethyl -4,6-diethylbenzene;

1,3-bis (bromomethyl -2,4,5-trimethylbenzene; 1,2,4-tris(bromomethyl) -3 ,5 ,6-trimethylbenzene; 1,3-bis (bromomethyl) -2-methyl-5-tert.-butyl-benzene 1,3-bis(bromomethyl -2-ethyl-5-tert.-butylbenzene; l,3-bis(bromomethyl) -2-methyl-4-tert.-butylbenzene 3,5 -bis (bromomethyl -4-methylcumene,

1,4-bis- (dibromomethyl -2,5-dichlorobenzene;

1,4-bis- (dibromomethyl -2,3,5,6-tetrabromobenzene; 1,2,4,5-tetrakisdibromomethyl) -3,6-dibromobenzene; 1,2,4,5-tetrakis- (dibromomethyl -3,6-dichlorobenzene; 1,3,5 -tris-'(dibrom0methyl) -2,4,6-tribromobenzene.

Of the compounds of this invention, particularly suitable are those wherein (a) RisCH Br;

(b) R is CH or Br;

(c) R is CH Br and n is 2 or 3;

(d) R is CH Br and R is CH or Br;

(e) 'R is CH Br, R is CH or Br and m is 2 or 3;

(f) R is OH Br, R is CH or Br and n is 2 or 3; and (g) R is CHBr R is Br and n is 2.

The polyalkylbrominated benzenes of Formula I can be obtained in accordance with conventional methods, 'v1z.,

(a) Nuclear halogenation of the corresponding polyalkyl benzenes in a suitable solvent, e.g., at room temperature, and subsequent side-chain bromination at a higher temperature, optionally under UV irradiation, the intermediate products being isolated or the production of the found reaction product is eflected in a single operating step;

(b) Bromomethylation of corresponding polyalkyl benzenes;

(c) Bromomethylation of corresponding polyalkyl benzenes and subsequent nuclear halogenation, e.g., at benzenes and subsequent nuclear halogenation, e.g., at a temperature of between 20 and 50 C. in a suitable solvent.

Especially suitable starting materials for the produc tion of the bromine compounds are durene, pseudocumene, mestiylene, the xylenes and the diethylbenzenes.

The brominated alkyl benzenes are employed in the novel polystyrene molding compositions in amounts of from 1-20% 'by weight, preferably 1-10% by weight, based on the styrene polymer, the exact amount being such that the molding compositions have a bromine content of at least 0.5% by weight. They can be employed individually or in a mixture of two or more compounds of Formula I. In addition to the brominated alkyl benzenes of Formula I, optionally the molding compositions can also contain one or more of chlorine compounds, antimony compounds, borates of alkaline earth metals or metals of Subgroup II of the Periodic Table of the Elements.

When employing chlorine compositions in the novel compositions of this invention, it is advantageous to employ those having a high chlorine content, in order to keep the quantities of chlorine compounds in the synthetic resin composition as low as possible. Suitable chlorine compounds are, for example, chlorinated paraflins of at least 15 carbon atoms, preferably 25-40 carbon atoms or chlorinated polyethylenes. The proportion of antimony compounds, e.g., antimony trioxide, should be kept as low as possible. In general, amounts of 12% by Weight are sufficient, based on the styrene polymer. Suitable borates are, for example, zinc borate and barium metaborate. The molding compositions can contain, in addition to the flame-retardant additives, other customary additives, e.g., one or more of stabilizers, lubricants, fillers, coloring agents and plasticizers.

Examples of styrene polymers employed in the novel compositions of this invention are polystyrene, poly-ozmethylstyrene, copolymers of styrene or a-methylstyrene and another monomer, e.g., acrylonitrile and esters of acrylic or methacrylic acid, containing at least 50% styrene or a-methylstyrene incorporated therein by polymerization. Impact-resistant styrene polymers containing elastomeric components and the so-called ABS (acrylonitrilebutadiene-styrene) polymers can also be employed. Impact-resistant styrene polymers can be obtained by mixing the styrene polymers with the elastomeric components or by grafting the styrene, optionally in a mixture with polymerizable monomers, onto the elastomeric component. It is, of course, also possible to employ mixtures of impact-resistant styrene polymers.

The molding compositions provided with the flame retardants of the present invention are especially suitable for the production of compact materials by extrusion or injection molding methods. In order to produce the selfextinguishing molding compositions, the bromine compounds can be added prior to, during, or after the polymerization of the styrene composition. However, advantageously, they are subsequently incorporated into the styrene polymer, optionally together with the chlorinecontaining additives and/or antimony trioxide and/ or the borates of the alkaline earth metals or transition metals or, individually in succession, on a rolling mill, in the extruder or in a masticator.

The molding compositions of this invention can also be added to styrene polymers containing expanding agents. Suitable expanding agents are hydrocarbons or halogenated hydrocarbons which are gaseous or liquid under ambient conditions, which do not dissolve the styrene polymer, and the boiling points of which are below the softening point of the polymer, e.g., propane, butane, pentane, hexane, cyclohexane, dichlorodifluoromethane, and trifluorochloromethane. The blowing agents can be employed in the expandable molding compositions in amounts of 2- 15% by weight, based on the styrene polymer.

The bromine compounds are, under storage conditions, entirely resistant to hydrolysis and odorless, and, under processing conditions, sufliciently thermally stable so that they are not yet degradated into corrosive fragments, as in the case of conventional bromoalkyl compounds.

The self-extinguishing effect of the additives in the molding compositions can be evaluated in accordance with the following test:

Vertically suspended testing pieces (strips x 10 x 1 mm.; strips 100 x 10 x 2 mm.; sheet 100 X 100 x 2 mm.) are subjected at their lower edges to a small, non-luminous Bunsen burner flame (flame length approximately 2 cm.) until they begin to burn. After removal of the flame, the after-burning time is determined in each case.

At least 5 ignition tests are conducted on each specimen. The afterburning times of the specimens which were in each case ignited five times were utilized as data. These data constitute a satisfactory criterion of the extent to which the polystyrene composition has been rendered 6 EXAMPLE 11 100 Parts by weight of an impact-resistant polystyrene and 10 parts by weight of l,3,5-tris(bromomethyl)-2,4,6- trimethylbenzene are processed into a strip of 1 mm. thickflameqetardant 5 ness as described in Example 1. The afterburning times Without further elaboration, it is believed that one aggi z i g k f 2 th f b skilled in the art can, using the pricelding descriptli tgn, ptitimes are g 0 e a ter ummg lize the present invention to its u est extent. e olowing preferred specific embodiments are, therefore, to gr g g fig i gj gf g 1:3 by welgilt g be construed as merely illustrative, and not limitative of Wei ht thereof th 2 y parts y the remainder of the disclosure in any way whatsoever. g Q er W1 parts. y welghtpf timony trioxide, in 100 parts by weight of an impact- EXAMPLE 1 resistalnt lpolystyrene, the afterburning times for a strip 1 100 Parts by weight of an impact-resistant polystyrene t 1e seconds containing 8.5% by weight of a butadiene-styrene copoly- The Pg ex amp1es can 2 repeated i slmllar mer and 4.5% by weight of parafiin oil, 5 parts by weight iff y Substltutmg the geneneauy F. of 1,2,4,5-tetrakis (bromomethyl)-3,6-dibromobenzene, 2 Sen reactants and/0F operatmg cfndltwns of the parts by weight of chlorinated parafiin (70% chlorine) verllztlon ig flflose m Preeedmg f e and 2 parts by weight of antimony trioxide are mixed 20 6 9 descnPtlfm one t' fl the d together, homogenized on a roll and comminuted. From eeslly ascertain the essential eharaetenstles. 9 the the resulting granules, pressed plates are produced and the g and wlthout dePaFtmg from the Splnt and test specimens are cut therefrom. The afterburning times :F can.make change? and modlfiea of the Strip of a thickness of 2 mm are in the burning 1011; of the invention to adapt it to varlous usages and test, 1-1-2-2-1-2 seconds. Admixing 7 parts instead of g i 1 d 5 parts by weight of 1,2,4,5-tetrakis(bromomethyl)-3,6- 1 c fi h dibromobenzene does not appreciably alter the afterburnn a e t ermoplastlc Polystyrene molding times ing composltion containing 1-20%, based on the styrene COMPARATIVE EXAMPLES polymer, of at least one brominated polyalkyl benzene, I the improvement wherein the brominated polyalkyl ben- Addlng, 1nstead of 5 parts by weight of l,2,4,S-tetrak1s Zene is a compound f the f l (bromomethyl)-3,6-dibromobenzene, 8 parts by weight of a bromination product of hexamethylbenzene containing Rm an average of 5.5 bromine atoms per molecule to the impact-resistant polystyrene of Example 1, afterburning times of 8-7-9-6-5 seconds are obtained.

An attempt to produce self-extinguishing test specimens from impact-resistant polystyrene by admixing thereto 1,2- n bis(dibromomethyl)benzene, 1,4-bis(dibromomethyl)benzene or 1,4-bis(bromomethyl)benzene, failed because the wherein R is bromomethyl or dibromomethyl; m is an bromine compounds decomposed at the processing teminteger from 2 to 4, inclusive; R is bromine or chlorine, peratures and inflicted noticeable damage on the processat least one R being ortho to each R and n is an integer ing machines. from 1 to 4.

EXAMPLE 2 2. A composition according to Claim 1 containing 100 Parts by weight of an impact-resistant polystyrene {1 by weight based on the Styrene Polymer of the with 8.5 by weight butadiene and 4.5% by weight of rommated F paraflin oil content, 7 parts by weight of 1,4-bis(dibromo- A molemg composltlon accordmg to Clalm 1 Where methyl)-2,5-dibromobenzene, 2 parts by weight of chlorim the ff i polyalkyl benzene compound has a nated paraflin (70% chlorine) and 2 parts by weight of composltlon PF of at 'E antimony trioxide are homogenized on a roll and pressed A composltlon according t0 Clalm 1 Whereln R 15 into sheets. The afterburning times of a strip of 2 mm. CHZBT- thickness are 2 2. 2 1 .2 seconds 2. 2 COmpOSltI-On 0f Clalm 1 wherein R is BI.

. composition according to Claim 1 wherein R is EXAMPLES 340 CH Br and n is 2 or 3. 100 Parts by weight of the impact-resistant polystyrene 5 7- A Composition according to Claim 1 wherein R is employed in Example 2, 2 parts by weight of chlorinated 5 CH Br and R is Br. parafiin chlorine), 2 parts by weight of antimony 8. A composition according to Claim 1 wherein R is trioxide and the parts by weight of various bromine com- CH Br, R is Br and m is 2 or 3. pounds set forth in Table 1 are pressed into sheets as de- 9. A composition according to Claim 1 wherein R is scribed in the preceding examples. The afterburning times Br and n is 2 or 3. are measured on a x 10 x 1 mm. strip and a 100 X 100 60 10. A composition according to Claim 2 wherein the x 2 mm. sheet. brominated polyalkyl benzene compound has a decompo- TABLE 1 Br content Afterburning times (sec.) Example number Part? il of mlxture weig 1; (percent) Strip Sheet 3 l,4-bis(bromomethyl)-2,5-dimethylbenzene 10 4. 1-22-1-1 1-2-1-2-3 4 1,3,5-tris(bromomethyl)-2,4,6-tribromobenzena 10 7.9 2-3-5-2-14 1-2-2-5 6 1,4-bis(bromomethyl)-2,3,5,6-tetramethylbenzene 8 3.6 2-1-2-2-3 1-2-1-2-2 g 1,2,4 lz-tetrakis(bromomethyl)-3,6-dibromobenzene g 3 1,4-b(s)(dibromomethyl)-2,5-dibromobenzene g 2-1-345 10 1,3,5-tris(bromomethyl)-2,4,6-tri-methy1benzene 6 31a a-2-1-1:2 i i i 7 sition point of at least 200 0., wherein R is CH Br and R is Br.

11. A composition according to Claim 10 wherein n is 2 or 3.

12. A composition according to Claim 11 wherein the brominated polyalkylbenzene is 1,2,4,5-tetrakis(bromomethyl)-3,6-dibromobenzene.

13. A composition according to Claim 1 wherein the brominated polyalkylbenzene is 1,3,5-tris(bromomethyl)- 2,4,6-tribromobenzene.

14. A composition according to Claim 1 wherein the brominated polyalkylbenzene is 1,2,4-t1'is(bromomethyl)- 3,5,6-tribromobenzene.

15. A composition according to Claim 1 wherein the brominated polyalkylbenzene is 1,4-bis(dibromomethyl) 2,5-dibromobenzene.

References Cited UNITED STATES PATENTS 3,331,797 7/1967 Kopetz et a1. 260-285 3,551,360 12/1970 Drcssler 260-2.5

8 3,658,634 4/1972 Yanagi et a1 161175 2,028,715 1/1936 Hanson 252-8.1 2,631,168 3/1953 Ross et al 260-618 2,676,927 4/1954 McCurdy et a1 260-25 3,058,926 10/1962 Eichhorn 26O2.5 3,168,580 2/1965' Adams 260651 3,372,141 3/1968 Dickerson et al. 26045.95 3,396,201 8/1968 Weil et a1 260648 3,419,626 12/1968 Pyne ct a1 260-651 3,420,786 1/1969 Weber et a1 2602.5 3,635,850 1/1972 Birkner et a1. 260-25 OTHER REFERENCES Hopif et al.: Chemical Abstracts, vol. 56, 1962, 399e.

DONALD E. CZAJA, Primary Examiner R. A. WHITE, Assistant Examiner US. Cl. X.R.

260--2.5 FP, 28.5 A, 28.5 B, 45.75 B, 45.75 R, 892 

